Chapter EN, Problem 13PQ

Interpretation Introduction

Interpretation:

$\Delta H_{\text{f}}^{\text{o}}$ of ${\text{NH}}_3$ in following reaction has to be determined.

  $4{\text{NH}}_3\left(g\right)+5{\text{O}}_2\left(g\right)\to 4\text{NO}\left(g\right)+6{\text{H}}_2\text{O}$

Concept Introduction:

Standard enthalpy of reaction is calculated by summation of standard enthalpy of formation of the product minus the summation of standard enthalpy of formation of reactants at the standard conditions. The expression to calculate the standard enthalpy of reaction $\left(\Delta H_{\text{rxn}}^{°}\right)$ is as follows:

  $\Delta H_{\text{rxn}}^{°}=\sum m\Delta H_{\text{f (products)}}^{°}-\sum n\Delta H_{\text{f (reactants)}}^{°}$

Here,

  m is the stoichiometric coefficient of the product.

  n is the stoichiometric coefficient of reactant.

  $\Delta H_{\text{f}\left(\text{reactants}\right)}^{°}$ is the standard enthalpy of reactant formation.

  $\Delta H_{\text{f}\left(\text{products}\right)}^{°}$ is the standard enthalpy of product formation.